New Balance Sigma Harmony BOA Sprint Running Track Spikes Black/​Green Colour: Green Code: MC42NB31398 Product Detail: New Balance low profile slip on running track spikes with BOA® lacing system for an adjustable fit. Synthetic and textile upper. Textile lining. Sock-like construction for the ultimate locked-down fit. Boa lacing system - a micro-adjustable closure dial that equates to a one millimeter of tension with each click. Lightly padded ankle. Lightweight Pebax® outsole. 8 spike configuration. New Balance Sigma Harmony BOA Sprint Running Track Spikes Black/Green